1. Field of Invention
The present invention relates to a pulse receiving circuit and a pulse wireless communication device using ultra-wide band.
2. Related Art
Ultra-wide band (UWB) communication is a communication system which provides data communication by using extremely wide frequency band. Examples of the communication system using UWB signals in a wide band include spectrum diffusion method, orthogonal frequency division multiplex (OFDM), and other known methods, and further include impulse radio (IR) system which uses pulses having extremely short periods. The IR system used in the UWB communication is particularly called UWB-IR. According to the UWB-IR system, modulation and demodulation can be performed not by conventional modulation method but only by time base operation, and improvement over simplification of circuit and reduction of power consumption is expected.
In the pulse communication having large occupation frequency band width, however, the communication is affected by the presence of extremely strong interference signals having narrow band.
For example, according to a pulse receiving device using envelope detection such as rectification detection proposed in JP-A-2005-252740, the structure for achieving rectification detection has a simple circuit and performs low power consumption operation. However, this structure detects all frequency components and therefore requires band pass filter for removing interference signals. In this case, the cost and size increase. The technology disclosed in JP-A-2003-110466 is a method for reducing the effect of interference signals by using diffusion codes instead of the band pass filter. However, pulses having a rate higher than necessary bit rate need to be generated so as to provide the necessary bit rate. In this case, power consumption increases. Furthermore, when a process for removing interference signals is executed by inverse diffusion method in a digitized manner, a multi-bit AD converter needs to be provided to cope with large interference signals. In this case, circuit scale and power consumption increase.
JP-A-2005-39526 discloses a method for executing synchronous detection by using correlation with receiving pulse waveforms.
According to this method, interference waves other than desired pulses can be removed by performing correlation calculation without the need for providing band pass filter. However, highly accurate timing process is required at the time of execution of correlation calculation. For satisfying this requirement, clock source having high accuracy and low jitter is needed. Moreover, a complicated pulse position synchronous circuit is required, which increases power consumption.